Michelle Obama's appearances in sleeveless outfits have inspired some women to start toning their arms.

She's on the March cover of Vogue in a sleeveless silk sheath. Then there was the purple sleeveless Narciso Rodriguez she wore to the president's joint session of Congress on Tuesday. And she's on the cover of the latest People magazine in a lacy pink number, also without sleeves.

Those toned arms are becoming a trademark. And a source of inspiration for some women.

Rylan Duggan, a personal trainer who runs Go Sleeveless, a blog that instructs women how to tone up flabby arms and "eliminate bat wings," said that in addition to asking how to get "Madonna arms" or "Kelly Ripa arms," clients are now asking about getting "Obama arms."

"The Obama effect has been that women of all ages have been inspired to take responsibility for their health and their body," said Duggan. "As the first lady of the United States, at 44 years old, and with two young children, Mrs. Obama has shown the world that you are never too busy to take care of yourself and look good doing it too," he said.

Exercise advocates are also fans. "She's a great role model," said Jessica Matthews, a continuing education coordinator for the American Council on Exercise. "Women shy away from strength training, because they're afraid of big muscles. She shows nice toned arms and that it's not going to lead to this myth of a bodybuilder type."

Women don't have the hormones to develop huge muscles by strength training, unless they're working out to an extreme or taking steroids, Matthews said.

Obama has said she exercises in 90-minute workout three times a week with a personal trainer. The first lady told People magazine that during an average day in the White House, she and the president get up at 5:30 a.m. and usually work out and have breakfast.

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When Obama emerged with uncovered arms on Tuesday, some grumbled about her showing too much skin on an occasion where other women were wearing long sleeves or suits.

Boston Herald columnist Lauren Beckham Falcone wrote to Obama, "It's February. Going sleeveless in subzero temperature is just showing off. All due respect."

But others were amazed, like 25-year-old Jessie Rosen. After seeing Obama at the speech Tuesday, she went to the Adidas store in New York and bought two five-pound dumbbells. "It was her arms being so toned in spite of her life," she said.

"This woman is redecorating White House, trying to raise two children and backseat driving the nation," Rosen said. "She seems to have time to keep her arms toned, so why can't I?"

It's only the second day of Rosen's new dumbbell routine. She does 15 minutes with four to five different exercises in front of her television, before going to bed. She hopes the arm exercises will get her ready for beach season and upcoming weddings.

But personal trainers say arm exercises alone are not enough to get toned arms. First, a person has to get rid of body fat from the body, meaning "you can't spot reduce and just eliminate fat from the arms," Duggan said.

Also, an exercise program has to target all major muscles of the body.

Personal trainer Matthews recommends moderate intensity cardio for 30 minutes, five times a week or vigorous intensity cardio for 20 minutes, three times a week.

Both cardio exercises and strength training are needed to speed up metabolism and burn body fat.

"Even if the goal is just the upper body, you want to train all major muscles," said Matthews. "If you fail to strengthen the entire body, it limits lean mass. When we strength train, we are building lean body mass and decreasing body fat."

Strength training increases muscle mass and revs up the body to burn fat at a higher rate, allowing for the lean muscle definition to show. Matthews recommends strength training twice a week, on nonconsecutive days to allow muscles to repair themselves.

"Women are just really terrified of weights," she said. "They're on cardio machines, elliptical for 60 minutes and wondering why they don't see definition and tone. The missing link is strength training."

The arm exercises sculpt the muscle underneath, which should protrude as the fat fades.

It's unclear what kind of exercises Obama does to maintain her buff arms, but it appears to be both back and arm workouts, said Michele Vourliotis, author of "Amazing Arms: Get Toned Triceps, Beautiful Biceps, and Sexy Shoulders in Just Minutes a Day."

"She may be working out on machine, dumbbells, bands or using her body weight," Vourliotis said. Pick the option that seems most suitable to you, she advised.

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So how does a normal woman, who doesn't have a personal trainer or healthy meals from the White House chefs, get tight and taut biceps?

For beginners, Vourliotis recommends getting a suitable set of dumbbells (five pounds or more) and doing 12 to 15 of each exercise -- bicep curls, tricep kickbacks to exercise the back of the arm, shoulder and lateral raises. Visit the American Council on Exercises library for detailed instructions on these arm exercises.

Everyone's body is different and the definition in the arms can take a while to show, so don't get discouraged if the results don't show after just two weeks, trainers said.

"Certainly with strength training, you see great benefits in weights you can lift, within four to six weeks," Matthews said. "When it comes to starting developing muscle mass, it really varies. There's not a specific timeline."

Another component is to maintain a healthy weight, said Marisa Moore, a registered dietitian and spokeswoman for the American Dietetic Association.

"Focus on a nice, balanced diet, with lean protein, whole grains, fruits and vegetables, that's the way to maintain a healthy physique," she said. "When you're trying to maintain muscles, choose lean protein, like fish, chicken without the skin, eggs, beans. Those are great sources of protein."

The protein portions should be four ounces during a meal.

It sounds complex, but Duggan is optimistic that women of any age, no matter how saggy her arms are, can improve.

"You can have toned and sexy arms at any age regardless of your current fitness level or how bad your arms are sagging right now," he said.